Revealing the Dimeric Crystal and Solution Structure of β-Lactoglobulin at pH 4 and Its pH and Salt Dependent Monomer–Dimer Equilibrium

Sanaullah Khan, Richard Ipsen, Kristoffer Almdal, Birte Svensson, Pernille Harris*

*Corresponding author for this work

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Abstract

The dimeric structure of bovine β-lactoglobulin A (BLGA) at pH 4.0 was solved to 2.0 Å resolution. Fitting the BLGA pH 4.0 structure to SAXS data at low ionic strength (goodness of fit R-factor = 3.6%) verified the dimeric state in solution. Analysis of the monomer–dimer equilibrium at varying pH and ionic strength by SAXS and scattering modeling showed that BLGA is dimeric at pH 3.0 and 4.0, shifting toward a monomer at pH 2.2, 2.6, and 7.0 yielding monomer/dimer ratios of 80/20%, 50/50%, and 25/75%, respectively. BLGA remained a dimer at pH 3.0 and 4.0 in 50–150 mM NaCl, whereas the electrostatic shielding raised the dimer content at pH 2.2, 2.6, and 7.0, i.e., below and above the pI. Overall, the findings provide new insights into the molecular characteristics of BLGA relevant for dairy product formulations and for various biotechnological and pharmaceutical applications.
Original languageEnglish
JournalBiomacromolecules
Volume19
Pages (from-to)2905-2912
ISSN1525-7797
DOIs
Publication statusPublished - 2018

Cite this

@article{51eeeea1bea0481d92aa6c17cb874606,
title = "Revealing the Dimeric Crystal and Solution Structure of β-Lactoglobulin at pH 4 and Its pH and Salt Dependent Monomer–Dimer Equilibrium",
abstract = "The dimeric structure of bovine β-lactoglobulin A (BLGA) at pH 4.0 was solved to 2.0 {\AA} resolution. Fitting the BLGA pH 4.0 structure to SAXS data at low ionic strength (goodness of fit R-factor = 3.6{\%}) verified the dimeric state in solution. Analysis of the monomer–dimer equilibrium at varying pH and ionic strength by SAXS and scattering modeling showed that BLGA is dimeric at pH 3.0 and 4.0, shifting toward a monomer at pH 2.2, 2.6, and 7.0 yielding monomer/dimer ratios of 80/20{\%}, 50/50{\%}, and 25/75{\%}, respectively. BLGA remained a dimer at pH 3.0 and 4.0 in 50–150 mM NaCl, whereas the electrostatic shielding raised the dimer content at pH 2.2, 2.6, and 7.0, i.e., below and above the pI. Overall, the findings provide new insights into the molecular characteristics of BLGA relevant for dairy product formulations and for various biotechnological and pharmaceutical applications.",
author = "Sanaullah Khan and Richard Ipsen and Kristoffer Almdal and Birte Svensson and Pernille Harris",
year = "2018",
doi = "10.1021/acs.biomac.8b00471",
language = "English",
volume = "19",
pages = "2905--2912",
journal = "Biomacromolecules",
issn = "1525-7797",
publisher = "American Chemical Society",

}

TY - JOUR

T1 - Revealing the Dimeric Crystal and Solution Structure of β-Lactoglobulin at pH 4 and Its pH and Salt Dependent Monomer–Dimer Equilibrium

AU - Khan, Sanaullah

AU - Ipsen, Richard

AU - Almdal, Kristoffer

AU - Svensson, Birte

AU - Harris, Pernille

PY - 2018

Y1 - 2018

N2 - The dimeric structure of bovine β-lactoglobulin A (BLGA) at pH 4.0 was solved to 2.0 Å resolution. Fitting the BLGA pH 4.0 structure to SAXS data at low ionic strength (goodness of fit R-factor = 3.6%) verified the dimeric state in solution. Analysis of the monomer–dimer equilibrium at varying pH and ionic strength by SAXS and scattering modeling showed that BLGA is dimeric at pH 3.0 and 4.0, shifting toward a monomer at pH 2.2, 2.6, and 7.0 yielding monomer/dimer ratios of 80/20%, 50/50%, and 25/75%, respectively. BLGA remained a dimer at pH 3.0 and 4.0 in 50–150 mM NaCl, whereas the electrostatic shielding raised the dimer content at pH 2.2, 2.6, and 7.0, i.e., below and above the pI. Overall, the findings provide new insights into the molecular characteristics of BLGA relevant for dairy product formulations and for various biotechnological and pharmaceutical applications.

AB - The dimeric structure of bovine β-lactoglobulin A (BLGA) at pH 4.0 was solved to 2.0 Å resolution. Fitting the BLGA pH 4.0 structure to SAXS data at low ionic strength (goodness of fit R-factor = 3.6%) verified the dimeric state in solution. Analysis of the monomer–dimer equilibrium at varying pH and ionic strength by SAXS and scattering modeling showed that BLGA is dimeric at pH 3.0 and 4.0, shifting toward a monomer at pH 2.2, 2.6, and 7.0 yielding monomer/dimer ratios of 80/20%, 50/50%, and 25/75%, respectively. BLGA remained a dimer at pH 3.0 and 4.0 in 50–150 mM NaCl, whereas the electrostatic shielding raised the dimer content at pH 2.2, 2.6, and 7.0, i.e., below and above the pI. Overall, the findings provide new insights into the molecular characteristics of BLGA relevant for dairy product formulations and for various biotechnological and pharmaceutical applications.

U2 - 10.1021/acs.biomac.8b00471

DO - 10.1021/acs.biomac.8b00471

M3 - Journal article

VL - 19

SP - 2905

EP - 2912

JO - Biomacromolecules

JF - Biomacromolecules

SN - 1525-7797

ER -